.. _media: Media ===== Falcon allows for easy and customizable internet media type handling. By default Falcon only enables a single JSON handler. However, additional handlers can be configured through the :any:`falcon.RequestOptions` and :any:`falcon.ResponseOptions` objects specified on your :any:`falcon.API`. .. note:: To avoid unnecessary overhead, Falcon will only process request media the first time the media property is referenced. Once it has been referenced, it'll use the cached result for subsequent interactions. Usage ----- Zero configuration is needed if you're creating a JSON API. Just access or set the ``media`` attribute as appropriate and let Falcon do the heavy lifting for you. .. code:: python import falcon class EchoResource(object): def on_post(self, req, resp): message = req.media.get('message') resp.media = {'message': message} resp.status = falcon.HTTP_200 .. warning:: Once `media` is called on a request, it'll consume the request's stream. Validating Media ---------------- Falcon currently only provides a JSON Schema media validator; however, JSON Schema is very versatile and can be used to validate any deserialized media type that JSON also supports (i.e. dicts, lists, etc). .. autofunction:: falcon.media.validators.jsonschema.validate If JSON Schema does not meet your needs, a custom validator may be implemented in a similar manner to the one above. Content-Type Negotiation ------------------------ Falcon currently only supports partial negotiation out of the box. By default, when the ``media`` attribute is used it attempts to de/serialize based on the ``Content-Type`` header value. The missing link that Falcon doesn't provide is the connection between the :any:`falcon.Request` ``Accept`` header provided by a user and the :any:`falcon.Response` ``Content-Type`` header. If you do need full negotiation, it is very easy to bridge the gap using middleware. Here is an example of how this can be done: .. code-block:: python class NegotiationMiddleware(object): def process_request(self, req, resp): resp.content_type = req.accept Replacing the Default Handlers ------------------------------ When creating your API object you can either add or completely replace all of the handlers. For example, lets say you want to write an API that sends and receives MessagePack. We can easily do this by telling our Falcon API that we want a default media-type of ``application/msgpack`` and then create a new :any:`Handlers` object specifying the desired media type and a handler that can process that data. .. code:: python import falcon from falcon import media handlers = media.Handlers({ 'application/msgpack': media.MessagePackHandler(), }) api = falcon.API(media_type='application/msgpack') api.req_options.media_handlers = handlers api.resp_options.media_handlers = handlers Alternatively, if you would like to add an additional handler such as MessagePack, this can be easily done in the following manner: .. code-block:: python import falcon from falcon import media extra_handlers = { 'application/msgpack': media.MessagePackHandler(), } api = falcon.API() api.req_options.media_handlers.update(extra_handlers) api.resp_options.media_handlers.update(extra_handlers) Supported Handler Types ----------------------- .. autoclass:: falcon.media.JSONHandler :members: .. autoclass:: falcon.media.MessagePackHandler :members: Custom Handler Type ------------------- If Falcon doesn't have an internet media type handler that supports your use case, you can easily implement your own using the abstract base class provided by Falcon: .. autoclass:: falcon.media.BaseHandler :members: :member-order: bysource Handlers -------- .. autoclass:: falcon.media.Handlers :members: .. _media_type_constants: Media Type Constants -------------------- The ``falcon`` module provides a number of constants for common media types, including the following: .. code:: python falcon.MEDIA_JSON falcon.MEDIA_MSGPACK falcon.MEDIA_YAML falcon.MEDIA_XML falcon.MEDIA_HTML falcon.MEDIA_JS falcon.MEDIA_TEXT falcon.MEDIA_JPEG falcon.MEDIA_PNG falcon.MEDIA_GIF